Method of making an intervascular catheter system for implanting a radially expandable stent within a body vessel

Abstract

An intravascular catheter system and method of manufacture for implanting a radially expandable stent within a body vessel. The catheter system includes a shaft defining an inflation lumen in fluid communication with a balloon on the distal end of the shaft. A stent is mounted coaxially upon a balloon. The balloon has ridges impressed in the outline of the stent for at least a portion of the stent. The ridges are sized to receive the stent so as to cause the balloon to expand evenly and the stent to deploy uniformly. In an alternative embodiment the balloon may additionally have a polymeric surface layer exhibiting a higher coefficient of friction than the underlying material against the stent material. The surface layer may be provided as a high friction polymeric coating on a formed balloon or as a coaxial extrusion of a high friction polymeric material over the underlying balloon tubing material. In a further embodiment the balloon may have the polymeric surface layer exhibiting a higher coefficient of friction than the underlying material against the stent material but without the ridges.

What is claimed is: 
     
       1. A method of making an intravascular catheter system for implanting a radially expandable stent within a body vessel comprising: providing a catheter having a shaft defining an inflation lumen having a proximal end and a distal end, an inflatable balloon having a proximal end and a distal end, the balloon proximal end being sealingly affixed to the distal end of the shaft, the balloon being a fluid communication with the inflation lumen, the balloon having an outer diameter and a wall thickness, the balloon having a surface layer over an underlying layer, the surface layer having a lower melt temperature than the underlying layer such that heating the surface layer will not damage the underlying layer;   providing a stent, the stent having a thickness and being formed of a helically wound wire having longitudinally movable elements, the wire being wound into a zig-zag pattern; and   mounting the stent coaxially upon the outer diameter of the balloon, a portion of the stent thickness being recessed into the balloon by heating the stent to form areas sized to receive the helically wound wire and defined by a permanent first and second ridge deformation in the outer diameter of the balloon in the outline of the stent for receiving the portion of the stent thickness so as to reduce stent slippage or snagging and to cause the balloon to expand evenly and the stent to deploy uniformly.   
     
     
       2. A method of manufacture according to claim 1 wherein a temperature of 76 degrees C. is applied to the stent for one-and-one-half minutes. 
     
     
       3. A method of manufacture according to claim 1 wherein the ridges formed are less than 50 percent of the balloon wall thickness. 
     
     
       4. A method of manufacture according to claim 1 wherein the ridges are impressed into the surface layer, the surface layer having a sufficient coefficient of friction against the stent so as to reduce stent slippage and cause the balloon to expand evenly and the stent to deploy uniformly. 
     
     
       5. A method of manufacture according to claim 1 wherein the stent material is tantalum. 
     
     
       6. A method of manufacture according to claim 1 wherein the surface layer is provided of a material consisting of an elastomeric polymer. 
     
     
       7. A method of manufacture according to claim 4 including a step wherein the surface layer is coated upon the balloon. 
     
     
       8. A method of manufacture according to claim 4 including a step wherein the surface layer is coaxially extruded.